Conventional apparatus for engaging and holding articles of square cross section, such as for conveying hot glass containers between stages of a manufacturing process, include a chuck and a mechanism for lowering the chuck over the container (or raising the container into the chuck). The chuck has an internal diameter slightly greater than the diagonal dimension of the container, and an internal valve plate for abutment with the closed end of the container. A vacuum is applied to the valve plate through the spindle that carries the chuck, so that the container whose end is in abutment with the valve plate is held by suction against the valve plate. The chuck and spindle may then be lifted and/or lowered for conveying the container to a subsequent work station. Since the containers are normally in defined position but not in defined angular orientation, the chuck cavity must be cylindrical rather than square to accommodate angular misorientation of the containers. However, spacing between the flat sidewalls of the square container and the opposing internal surface of the chuck pocket provide an open area for air flow, and increase potential for loss of holding vacuum at the valve plate.
Although apparatus of the described character have performed satisfactorily, improvements remain desirable. For example, the leakage of air around the end of the container and the portion of the chuck cavity that surrounds the container sidewall can cause loss of holding force at the valve plate. It is therefore a general object of the present invention to provide a device for accommodating non-orientation of the container cross sections with the chuck while improving vacuum holding force applied by the chuck to the container.